Spatiotemporal pattern formation in E. coli biofilms explained by a simple physical energy balance

Area of Science:

• Microbiology
• Biophysics
• Systems Biology

Background:

• Bacterial biofilms offer survival advantages, but formation mechanisms remain unclear.
• Motility and chemotaxis are often cited as drivers of biofilm development.
• Understanding biofilm organization is crucial for controlling bacterial communities.

Purpose of the Study:

• Investigate the spontaneous formation of spatial patterns in Escherichia coli biofilms.
• Determine if physical processes, independent of motility, govern biofilm architecture.
• Develop and validate a physical model for biofilm pattern emergence.

Main Methods:

• Observed spatial pattern formation in non-motile Escherichia coli biofilms.
• Developed a minimal physical model based on phase separation principles.
• Tuned cell-cell and cell-surface interactions by modifying bacterial surface appendages (e.g., F pilus).

Main Results:

• Regular spatial patterns emerged in biofilms formed by non-motile bacteria.
• A phase separation model accurately described the observed patterns.
• Modifying surface appendages altered pattern formation, confirming the model's predictions.
• F pilus-expressing cells influenced wild-type cells' pattern incorporation.

Conclusions:

• Physicochemical interactions (cell-cell and cell-surface) are sufficient to drive organized biofilm spatial structures.
• Phase separation provides a viable mechanism for emergent order in bacterial communities.
• This work challenges motility-centric views and highlights the role of biophysics in biofilm formation.